Ten years after Pat Tillman's death by friendly fire, it’s still not certain who shot the NFL player-turned-Army-corporal in Afghanistan. But one of the three Army Rangers who opened fire says he can’t shake the fact that he might be at fault.

"It would be disingenuous for me to say there is no way my rounds didn't kill him, because my rounds very well could have,” Steven Elliott said in an interview with ESPN that aired Sunday. Elliott, discussing the incident in the media for the first time, said he has been able to cope with the April 22, 2004, tragedy because of therapy. He said he was speaking out because he wanted to give hope to other soldiers suffering from post-traumatic stress disorder.

Elliott said the incident was his first firefight. Months later, he and the others who mistakenly fired at Tillman were demoted out of the elite Rangers unit.

“Even if somebody else was identified through forensic science as to have fired the ‘fatal shot,’ that doesn’t change how I feel,” Elliott said in the interview. “I still fired on a friendly position and that wouldn’t change my sense of responsibility.”

Elliot, now 33, left the Army in 2007. He told ESPN that he hasn’t spoken to the two other soldiers involved since early on. They declined to comment to ESPN.

Elliott also hasn’t spoken to Tillman’s family.

Asked what he would say to them if he did get the opportunity, Elliott replied, “You just want to tell them how sorry you are and how completely inadequate those words feel.”

Hindered by a setting sun and weak radio reception in a mountainous area, two caravans of soldiers fired upon each other after one of the groups was ambushed. Elliott said he followed the lead of his commander and fired at shadowy figures on a hillside. Those shadowy figures turned out to be Tillman, Bryan O’Neal and an Afghan contractor, who was also killed.

Tillman and his companions had been firing at an enemy position, but Elliott's truck of soldiers misinterpreted the gunfire, Army investigators determined.

O’Neal told ESPN in a televised interview that he wasn’t ready to think about or to forgive the Rangers who fired at him and Tillman.

“To forgive them would mean I have to acknowledge they exist, and to me, they are nothing. All of them,” he said. “Their lack of taking that five seconds to really understand what they are shooting at -- two people died and it changed my life.”

Tillman, an NFL defensive back, was celebrated as a hero after declining a contract extension from the Arizona Cardinals to join the Army eight months after the Sept. 11, 2001, terrorist attacks.

Tillman's patrol was charged with killing or capturing suspected "high-value" Taliban and Al Qaeda targets along the border with Pakistan. He had conducted previous patrols in the Spera district, and in one village, he became known as the soldier who handed out small sums of cash -- $2 for children and $10 for men -- and small, hand-cranked radios.

His death at age 27 drew national attention, and he was hailed as a hero who had been killed by enemy fire. After a month, however, the Army disclosed he had been killed accidentally by U.S. troops.

Now, Tillman's widow, Marie Tillman, runs a foundation in his name that awards education scholarships to veterans. In an interview with the Arizona Republic, Marie Tillman said this month that she’s found a balance in her life. She has remarried but says Pat’s legacy is always close by.

"The impact of his decisions and the way he lived his life and just ... who he was, affected many, many people," Marie Tillman said. "[But] I can still have my relationship with him and my feelings about the impact that his life had on me and sort of bring all those things together."